Nasa point out that the cold, the man and the atmosphere are the three guilty of arctic ozone hole.
A combination of extreme cold temperatures, man-made chemicals and a stagnant atmosphere were behind what became known as the Arctic ozone hole of 2011, a new NASA study finds.
Even when both poles of the planet undergo ozone losses during the winter, the Arctic’s ozone depletion tends to be milder and shorter-lived than the Antarctic’s. This is because the three key ingredients needed for ozone-destroying chemical reactions —chlorine from man-made chlorofluorocarbons (CFCs), frigid temperatures and sunlight— are not usually present in the Arctic at the same time: the northernmost latitudes are generally not cold enough when the sun reappears in the sky in early spring. Still, in 2011, ozone concentrations in the Arctic atmosphere were about 20 percent lower than its late winter average…>>>more